The proposed law is intended to provide legal protections for farm workers.
protections means various ways of protecting farm workers.
This might include: providing them with gloves, drinking water, and accessible toilets during working hours. Or it could be about working hours, etc.
Each of those items would be an example of a protection.
The proposed law is intended to provide legal protection for farm workers.
protection with no s, or used as what we call an abstract noun refers to the general idea of protection and does not spell out or enumerate what specific protections the law provides.
So depending on what you want to say, you can use either, but with different meanings.
US Law The Migrant & Seasonal Agricultural Worker Protection Act
Title II — Migrant Agricultural Workers Protections [specific]
Sec. 201. Information and recordkeeping requirements.
Sec. 202. Wages, supplies, and other working arrangements.
Sec. 203. Safety and health of housing.
Please note: proposed laws provide protection or protections.
Saying legal here is redundant.