"requirement has been" is a valid phrase in written English.
You can use it express that something has already been done or fulfilled. For example, "The training requirement has been completed."
These results clearly suggest that C/EBPβ is required for stress-induced granulopoiesis; indeed, this requirement has been verified in other mouse models and in a zebrafish model.
That requirement has been relaxed.
Under deregulation, that requirement has been lost.
The new requirement has been in effect since August.
Enforcement of the requirement has been delayed several times.
The effect of this requirement has been to keep good jobs in America.
The scope of the exchange trading requirement has been the focus of the debate for months.
On many of those special fares, the Saturday night stay requirement has been dropped for the extent of the sale.
Now the Math A Regents exam, a graduation requirement, has been set aside as improperly prepared and aligned.
The Saturday night stay requirement has been a buttress of the airline fare structure for over 20 years.
But critics say the requirement has been so watered down that it is unlikely to have major impact.
