This article is from the 3b1 computers FAQ, by John B. Bunch with numerous contributions by others.
The lpadmin(1M), accept(1M), and reject(1M) commands require the user to be logged in as (or su'd to) user "lp". Being root will not work.
# su lp $ disable lp1 $ /usr/lib/lpadmin -plp1 -mdumb -v/dev/lp $ enable lp1
 
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