Arguments that terror prosecutions are criminalizing protected speech took another hit Wednesday, when the First Circuit Court of Appeals upheld terror-support convictions against Tarek Mehanna.

Mehanna is serving 17½ years in prison after a Boston jury convicted him in 2011 of conspiracy to provide material support to al-Qaida, conspiracy to commit murder abroad, providing material support to terrorists, and lying to federal investigators.

Likening terrorism to a “modern-day equivalent of the bubonic plague,” the First Circuit Court of Appeals found jurors had ample grounds to find Mehanna’s activities crossed the line into illegal material support. The ruling by Circuit Judge Bruce M. Selya acknowledged a delicate balance between “vital national security concerns and forbidden encroachments on constitutionally protected freedoms of speech and association.”

But the evidence supports the verdict and Mehanna’s sentence because his work was done in coordination with al-Qaida in an attempt to benefit the terrorist group.

The appellate court at times took a dismissive tone in addressing Mehanna’s arguments to overturn his conviction. Some were cast aside as “meritless,” while others were described as “convoluted theories” and “fishing in an empty stream.”

Arguments offered in amicus, or friend of the court, briefs by Mehanna supporters including the American Civil Liberties Union (ACLU) also found little traction. In many cases, the external briefs raised issues Mehanna had not. “The law is settled that amici cannot ordinarily introduce into a case issues not briefed and argued by the appellant,” the ruling said.

Mehanna’s case drew sympathy from Islamist groups and others. ACLU Massachusetts Executive Director Nancy Murray wrote after the conviction that Mehanna’s case proved that, “There is a Muslim exception to the First Amendment,” and that Muslims were being prosecuted for “thought crime.”

The Council on American-Islamic Relations (CAIR) Chicago chapter offered a similar claim, publishing an intern’s article which cast Mehanna as a victim of overzealous FBI surveillance because he is a Muslim. The Muslim Public Affairs Council (MPAC) reposted a Guardian article on its Facebook and Twitter accounts titled, “Tarek Mehanna: Punished for Speaking Truth to Power.”

But the appellate court stood by the jury’s verdict in rejecting such arguments.

Mehanna came under investigation in 2006. By then, he already had traveled to Yemen in hopes of reaching a terrorist training camp. When that didn’t work, he returned to Sudbury, Mass., where he began translating and posting material supporting al-Qaida and “Salafi-Jihadi perspectives,” the court wrote.

Jihad may have violent and non-violent interpretations, the court noted, but “the record makes clear that the defendant used the term to refer to violent jihad–and that is the meaning that we ascribe to it throughout this opinion.”

Evidence showed Mehanna’s work was “in response to Al-Qa’ida’s call,” prosecutors wrote, “and that he was pleased to be associated with Al-Qa’ida through his work.”

Mehanna’s supporters rejected the appellate ruling just as they rejected the verdict. “The fundamental problem with the [appellate] ruling is that it allows the government to prosecute unpopular political speech,” ACLU attorney Alex Abdo told the Boston Globe.

The argument that Mehanna merely engaged in protected speech can only be accepted by “looking at the evidence through rose-colored glasses…” the court ruled. “His coconspirators testified that [Mehanna] persistently stated his belief that engaging in jihad was ‘a duty upon a Muslim if he’s capable of performing it,’ and that this duty included committing violence. The evidence further showed that, following United States intervention in Iraq, the defendant concluded ‘that America was at war with Islam,’ and saw American ‘soldiers as being valid targets.'”

This case marks at least the third significant prosecution in which appellate courts dismissed claims by defendants and their allies that free speech was being criminalized. In the case of the Humanitarian Law Project, the U.S. Supreme Court found that free speech rights don’t apply when the speech is used in coordination with a terrorist group to provide a service. The Fifth Circuit Court of Appeals similarly found that speech was used to show the defendant’s intent to help a known terrorist group in a case involving Hamas support.

Mehanna’s attorneys also argued that jurors were unduly influenced by graphic videos and accounts of al-Qaida attacks. The court acknowledged that there is no clear formula to balance the prosecution’s need to show the defendant’s awareness and intent against “piling on” in a way that prejudices the jury. The trial judge had witnesses describe some of the more graphic imagery rather than show it to jurors, and “evinced a keen awareness of the First Amendment issues” in his rulings and jury instructions, the appellate court ruled.

The material was relevant, however, because Mehanna was “inspired by terrorist rants, developed an anti-American animus, which culminated in his decision to travel to Yemen to join in al-Qa’ida’s struggle.” And Mehanna claimed that his beliefs precluded him from attacking Americans anywhere. Prosecutors could use the al-Qaida videos and Internet material to show that was not true, the court ruled.

“It should not surprise a defendant that proof of his participation in conspiracies to provide material support to terrorist organizations and to kill Americans here and abroad will engender the presentation of evidence offensive to the sensibilities of civilized people…,” the ruling said. “Terrorism trials are not to be confused with high tea at Buckingham Palace.”