Non-competition clause as a restrictive covenant in the employee's contract

Good morning.

An American company is working as an advisor for the Dubai government. The company has got employees to sign a non-competition clause document, prohibiting them from working for the same clients for a period of 1 year.

Now, employees resigned and might work directly or indirectly with the same clients. The company is threatening to sue the former employees for non-compliance with that clause and make them obtain the company's legal authorization to do such work.

Can you please advise the level of legality and also what is the appropriate next step?