What is the biggest challenge a recruitment specialist faces in GCC countries?

From what I have heard from other recruiters here, following are some of the common challenges faced: 1.
Labour laws keep changing and could affect recruitment strategies.
2.
Employment contracts (or changes in these contracts) between countries can affect target talent pool.
3.
Visa Processing can take time based on various criteria.
Also as Zubair rightly said, a lot of countries are looking at employing locals to balance the ratio of Locals to Expats employees..

In countries like Saudi Arabia and United Emirates - because of the new labor laws.
I think the biggest challenge is to keep up with those regulations of hiring X no.
of locals in your company more commonly known as Emiritization or Saudization.
There are different other challenges too.
But if we're talking about biggest challenge that is specific to these countries - it has to be this one.