Disabilities and Accommodation: Can a Landlord Reject a Request for Building Modifications Due to Disability

My question involves landlord-tenant law in the State of: California

1. If a tenant with a severely autistic child prone to Injurious behaviors such as head banging against doors and windows requests the landlord to please install safety bars or grills against all windows and French glass doors, can the landlord reject the request ?

2. Is it legal to bar windows with grills in California ?

Disabilities and Accommodation: Can a Landlord Reject a Request for Building Modifications Due to Disability