(AFP) - France's top constitutional court is on Friday to decide whether it approves President Emmanuel Macron's contentious pensions reform after months of protests against the legislation.

If the Constitutional Council gives its green light for the core parts of the bill, the centrist 45-year-old leader hopes to sign the changes into law immediately, clearing the way for them to be implemented by year-end.

Here is what you need to know:

- Two decisions -

Nine people sit on France's Constitutional Council, whose job it is to decide whether a law is in line with the constitution.

At the moment, it is made up of six men and three women.

Three members are named by the president, another three by the speaker of the lower-house National Assembly and the last three by the president of the upper-house Senate.

All sit for a non-renewable nine-year term and three fresh members are named every three years.

The council is expected to decide by the end of the day whether to approve partially, accept fully or reject Macron's flagship pensions overhaul, whose headline measure is to push back the retirement age from 62 to 64.

Left-wing and independent lawmakers, who fiercely oppose the plan, are also hoping the council will approve a bid to organise a referendum on an alternative law to limit the retirement age to 62 -- as is currently the case.

The council's decisions will be binding.

- Probable partial approval -

Many believe the pensions reform, which has been presented as a budget bill, will be partially approved.

"The council will likely follow the course it always had -- not to counter big social or societal reforms," constitutional expert Laureline Fontaine told AFP.

Under that scenario, certain parts of the law could be rejected as being irrelevant to a budget law.

This could apply to a so-called "senior index" aimed at encouraging firms to employ more people older than 55.

But that would not be a huge blow to the government, who could argue that the reform's core change of raising the retirement age to 64 has been approved.

It is this part of the law that has outraged unions and protesters, especially after Prime Minister Elisabeth Borne used a controversial executive power to force it through parliament without a vote last month.

Constitutional experts say they think a full approval of the law is improbable.

- Total rejection a long shot-

On Tuesday and Thursday, left-wing lawmakers visited the council to urge them to completely ban the reform.

They argue that the government's unorthodox method of resorting to a budget law to pass a pension reform, as well as invoking controversial article 49.3 of the constitution to bypass a parliament vote, is grounds for it to be thrown out.

Public law professor Elina Lemaire said this was a long shot.

"The council would have to go and analyse the government's conscience, which it has always refused to do," she said.

Didier Maus, a constitutional expert, said one hope for opponents of the pension overhaul was that the council see in the reform a form of inequality, such as measures that discriminate against women or unskilled workers with long careers.

Critics of the bill say these groups will suffer if the new law is passed, but the government argues the changes are necessary to avoid the pensions system from falling into deficit over the coming decades.

- Referendum? -

It is unclear whether the council will approve starting a process towards a possible referendum on the opposition's draft law to limit the retirement age to 62.

Fontaine, the constitutional expert, said permission was "likely".

But the path towards an actual referendum would be long.

For any vote, the opposition would need to collect 4.8 million signatures from voters backing their proposal within nine months.

A referendum would only take place if both chambers of parliament refused to examine the bill in the next six months -- something regarded as unlikely.

© Agence France-Presse