President Kagame has denied charges he was involved in killings
The Rwandan parliament has voted to change the country's constitution to give former presidents immunity from prosecution, for life.
The amendment says that a former president cannot be prosecuted on charges for which he was not put on trial while in office.
The justice minister said the change would remove ambiguity in the old law.
Judges in France and Spain have accused President Paul Kagame of involvement in killings linked to the 1994 genocide.
In April, a Spanish judge said he had evidence that Mr Kagame was linked to the killing of Hutus after the genocide, sparking fury in Rwanda.
In 2006, a French judge accused Mr Kagame of ordering the attack against the plane carrying former President Juvenal Habyarimana - whose death sparked the genocide.
President Kagame has always denied the charges and says Mr Habyarimana, a Hutu, was killed by Hutu extremists and blamed on his Tutsi rebels to provide the pretext for carrying out the genocide.
The BBC's Geoffrey Mutagoma in the capital Kigali says the constitutional amendment implies that serving heads of state can be prosecuted.
He says the immunity section is the most significant of more than 50 constitutional amendments which MPs have approved.
Another amendment says the constitution will now refer to the 1994 genocide as a "genocide committed on Tutsis".
Some 800,000 Tutsis and moderate Hutus were slaughtered by Hutu extremists.