La. Stat. tit. 13 § 3478
When there is a constable or duly appointed deputy constable not disqualified to act because of relationship, or unable to act on account of sickness or other cause, and who is willing to act, and who is personally present when conservatory writs are sued out, then and in these cases, the justice of the peace for whose ward said constable shall have been elected or appointed and qualified, shall employ said constable or his duly appointed deputy constable to the exclusion of the sheriff or his deputy, or a special deputy constable, to execute all orders, citations, summons, seizures, and writs in civil cases, and in such cases services made by other than said constable or his duly appointed deputy constable shall be void and of no effect.
La. R.S. § 13:3478