Legal Question in Landlord & Tenant Law in California

Almost certainly yes. A landlord has a legal right to access the premises under various circumstances. By placing a lock on both gates you have violated that right. In addition, if the landlord has even a half-way decent lease, it prohibits you from changing or adding locks, or at a minimum requires you to provide the landlord a key and/or combination. Tenants should never add or change locks without discussing it and making arrangements with their landlord first.