The convention seeks to reduce the number of Europeans traveling abroad to join Islamist groups.
"The draft additional protocol is a response to the increasing phenomenon of so-called foreign terrorist fighters," Lord John Tomlinson, member of the UK House of Lords, said while addressing the assembly.
He said that states must be in a position to take appropriate measures to fight terrorism, but there should be "no need for a trade-off between human rights and effective counter-terrorism actions."
The protocol aims to ensure that the measures taken to curb the flow of foreign fighters traveling from Europe to join jihadist groups abroad, do not violate basic human rights, such as the freedom of movement, the presumption of innocence or legal certainty.
France's recent decision to block five websites, without a court order, for allegedly promoting terrorism, was slammed by the Organization for Security and Co-operation in Europe as posing a "serious threat" to the freedom of expression.
On April 6, EU Justice Commissioner Vera Jouriva said that more than 6,000 Europeans could be fighting for radical Islamist groups in Syria alone.
Earlier this spring, French Prime Minister Manuel Valls forecasted that the total number of Europeans fighting alongside IS terrorists abroad could reach 10,000 by the end of 2015.
