Judges have two months since the final approval of the bill on May 30 to apply the law, which is expected to affect around 400 people including the former head of the regional government of Catalonia, Carles Puigdemont.
The aim was for arrest warrants and criminal charges filed against separatists to be annulled, even while appeals against the amnesty law are heard by higher courts -- a process that could take years.
But the courts must decide to apply the amnesty on a case-by-case basis, a laborious process that takes time.
"Political leaders and MPs are the masters of creating legislation but jurists are the masters of applying the law," Alfons Lopez Tena, a jurist and former pro-independence lawmaker in Catalonia's regional parliament, wrote in a recent article published in legal news website Confilegal.
If a judge "considers that the law, or one of its articles, violates European legislation, he can independently decide not to apply it, without the need for an appeal or a preliminary question", he added.
Socialist Prime Minister Pedro Sanchez, who had opposed the law in the past, agreed to grant the amnesty in exchange for obtaining support from Catalan separatist parties in parliament.
That support was essential for him to win reappointment for another four-year term in office after an inconclusive general election in July 2023.
Political crisis
The most high-profile beneficiary of the amnesty is expected to be Puigdemont who fled Spain shortly after the independence bid and now divides his time between Belgium and France.
While Puigdemont was Catalan regional leader, his administration pressed ahead with a referendum on independence on October 1, 2017, despite a ban by the Spanish courts.
Several weeks later, the Catalan parliament made a symbolic declaration of independence, prompting the central government to impose direct rule on the region.
The events triggered Spain's biggest political crisis since the advent of democracy following the 1975 death of dictator Francisco Franco.
Puigdemont had said he hoped to return to Spain soon but there is still a warrant for his arrest and a Spanish court is still investigating him for the alleged crimes of embezzlement and disobedience related to the secession bid.
He is also still under investigation for the alleged crime of terrorism over protests in 2019 against the jailing of several separatist leaders involved in the referendum that sometimes turned violent.
Judges have decided that arrest warrants will remain in force pending the resolution of any doubts about the legality of the amnesty law by higher courts.
'Legal adventures'
There is also a lack of consensus over if the amnesty covers embezzlement -- one of the main offences linked to the secession bid.
The issue is one of interpretation. The law allows the amnesty to be applied if the funds were used to finance the pro-independence process, but not if the money was taken for personal gain.
Spain's chief prosecutor, Alvaro Garcia Ortiz, argues the amnesty applies to all crimes including embezzlement but the four prosecutors handling Puigdemont's case disagree.
The prosecutor's office decided on Tuesday with 19 votes in favour and 17 against to back Garcia Ortiz's position.
But judges will have the last word as the amnesty law specifies that they will decide "its application to each specific case".
Catalan separatists consider the delays in applying the amnesty unjustified and are growing impatient.
Puigdemont's lawyer, Gonzalo Boyle, has sent a letter to the Court of Auditors -- the body charged with verifying public spending -- to ask that it annul "without further delay or legal adventures" the process against Puigdemont regarding the money the regional Catalan government allegedly used in the secession bid.
