LONDON — Employers are allowed to bar workers from wearing headscarves provided restrictions on religious garments are applied to employees of all faiths, the European Union’s top court ruled on Tuesday, in a decision that could shape the place of Islam in public life on the Continent.

In its ruling, the Luxembourg-based European Court of Justice said that internal regulations banning “the visible wearing of any political, philosophical or religious sign’’ did not constitute direct discrimination.

The court also said that, in the absence of a general ban on religious symbols, employers could not prevent a worker from wearing a headscarf simply because a customer demanded it.

The decision by the court comes as countries across Europe are grappling with how to accommodate huge numbers of migrants, many from predominantly Muslim countries in the Middle East and Asia. Nationalist, right-wing parties have seized on the issue of Muslim immigration to build support before elections in France, Germany, and the Netherlands.

The decisions of the European Court of Justice, which interprets the law for the 28-nation European Union, are binding on member states. Legal experts said the headscarves ruling could have far-reaching consequences for the balance between freedom of religion and the rights of companies across the bloc to put in place policies requiring religious neutrality.

The ruling followed advisory opinions in two separate cases that appeared somewhat contradictory. In a case in May, Juliane Kokott, an advocate general with the court, issued an advisory opinion saying that a company could prohibit a Muslim employee from wearing a headscarf provided that the policy applied to all religious attire and did not single out Islam.

That opinion came after a complaint by Samira Achbita, a Muslim woman in Belgium, who was fired as a receptionist for the international security services company G4S after she insisted that she be allowed to wear a headscarf at work.

Achbita sued the company, and the Belgian Court of Cassation asked the European Court of Justice for clarification about what European law required.

The Court of Justice concurred with the advisory ruling, saying that Achbita had not been subject to discrimination because the internal directive was broadly written and did not specifically address Islam.

The court said that it was up to the Belgian Court of Cassation to determine whether an employer had committed “indirect discrimination’’ if any directive ultimately affected “persons adhering to a particular religion or belief.’’

In a separate case, in July, Eleanor Sharpston, another advocate general with the European Court of Justice, issued an advisory opinion that a French company had engaged in unlawful discrimination when it dismissed a Muslim woman for wearing a headscarf when dealing with clients.

The woman, Asma Bougnaoui, lost her job at Micropole, an information technology consultancy, in 2009, after she refused to abide by the company’s request that she remove her headscarf when meeting with clients. Bougnaoui took her case to a French court, which referred it to the European Court of Justice.

In her advisory opinion, Sharpston said that the company’s decision to dismiss Bougnaoui had constituted “direct discrimination’’ based on religion or belief. Sharpston said there was no evidence to suggest that Bougnaoui had not been able to perform her job as a design engineer because she was wearing a headscarf.

Sharpston indicated, however, that if Bougnaoui had covered her face completely, the ruling would have been different, because eye-to-eye contact was considered important in Western business interaction.

In its ruling, the European court said it would be up to the French court to determine whether Bougnaoui’s dismissal was “appropriate and necessary,’’ in line with the ruling in Achbita’s case.

Rights advocates criticized Tuesday’s decision, saying that it undermined the guarantee of equality.

Maryam H’madoun, a policy adviser with the rights organization Open Society Foundations, said that in many EU member states, national law would still recognize that a ban on religious headscarves at work constituted discrimination.