Student Matt Zingarella was told to remove his pro-gun T-shirt on Monday by officials at Guilford High School in Guilford, Connecticut.
Zingarella's T-shirt included a picture of an assault weapon with the words: "I Plead The 2nd," an apparent reference to the Second Amendment.
Zingarella told CBS Connecticut that he was expressing his opposition to the new state gun law.
Connecticut Gov. Dannel Malloy signed a sweeping new gun control proposal into law on April 4.
The new law bans 100 different kinds of assault weapons, limits the capacity of ammunition magazines to 10 rounds, bans armor-piercing bullets and requires background checks for all gun purchases, reported CNN. The law also requires eligibility certificates when buying any rifle, shotgun or ammunition.
Zingarella says the shirt is not banned by the school dress code, but school officials say the dress code does bans shirts that disrupt the educational process.