Think twice before you obstruct, resist or oppose a process server, you may be committing a FELONY.

Federal Law Prohibiting Interference with Service of Process

Title 18 U.S.C. Section 1501
Whoever knowingly and willingly obstructs, resists or opposes any officer of the United States, or other person duly authorized, in serving, or attempting to serve or execute, any legal or judicial writ or process of any court of the United States...shall, except as otherwise provided by law, be fined not more than $300 or imprisoned not more than one year, or both.

Whoever Assaults or Wounds any officer or other person duly authorized, knowing him to be such officer or other person so duly authorized in serving or executing any such writ, rule, order, process, warrant, or other legal or judicial writ or process
Shall except as otherwise provided by law, be fined under this title or imprisoned not more than one year or both.

California State Law
Penal Code Section 242 and 243 Assault & Battery on a Peace Officer, Process Server, Employee of the Probation Dept., Custodial Officer, EMT, Animal Control Officer, Traffic Officer, etc.
When a battery is committed against the person of a peace officer, custodial officer, firefighter, emt, process server, et al in the performance of his or her duties the battery is punishable by a fine not exceeding two thousand dollars ($2,000.00) or by imprisonment in a county jail not exceeding one year or by both.