The most common and most likely answer to this crossword clue is the 9 letter word ORDINANCE
I've seen this crossword clue in The Guardian
O
R
D
I
N
A
N
C
E
More clues leading to the result ORDINANCE
- Decree one which Arsenal has put about
- Tory disrobed in and around church ceremony
- Priest in training ultimately ignored church law
- Regulation unfortunately constrained, lacking sanctions initially
- Bill or Bob keeps batting
- Ruling men replace head of banking with director
- Old Republican steps, perhaps to secure home rule
- Religious practice, one adopted by the big guns
- 16 Decree when 1 must enter 9 (9]
- India gripped by guns as ritual
Buddy explains!

The straight part
We know that "law" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case law = ordinance.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ORDINANCE mean?
ORDINANCE noun- A local law
- An edict or decree, authoritative order.
- A religious practice or ritual prescribed by the church.