Legal Question in Criminal Law in California

Only if you consent, they have a warrant, or if there is some "emergency." Keep your door locked.

The answer depends on what the circumstances are and what is being searched. If it's a residence, there better be consent or exigent (emergency) circumstances. If it's a car, slightly different rules apply, but they must have probable cause to search. If it's a person, they must justify the search by probable cause or have an ex eption to the warrant requirement.

Your question is just too broad for a definitive answer. Every search issue is unique and one fact can change the analysis. The entire situation would have to be reviewed by your attorney.