Syrian President Bashar al-Assad met US Senator John Kerry last week
Human Rights Watch has urged Syria to lift its state of emergency and abolish the State Security Court.
A report by the New York-based group describes the court as "one of Syria's main pillars of repression".
HRW also called on the EU and US to make human-rights improvements in Syria a condition for better diplomatic ties.
Syria was described by ex-US President George W Bush as part of the "axis of evil". But there have been recent moves to end its diplomatic isolation.
In July last year Syrian President Bashar al-Assad visited Paris.
Damascus was visited last week by three US delegations.
One was headed by Senator John Kerry, who said there was an opportunity for President Barack Obama's administration "to put in place a different approach".
The release of the HRW report coincides with a visit to Syria by European Union foreign policy chief Javier Solana.
The document accuses the State Security Court of staging "sham trials" to punish those seen as a threat to the state.
"It's a kangaroo court providing judicial cover for the persecution of activists, and even ordinary citizens, by Syria's security agencies," said HRW's Sarah Leah Whitson.
The report called on Syria to "decriminalise peaceful political activity".