Law-Rune Enforcer — ruling 1

Tokens that aren't a copy of something else don't have a mana cost. Anything without a mana cost normally has a mana value of 0.

Law-Rune Enforcer — ruling 2

If a permanent has {X} in its mana cost, X is considered to be 0.

Law-Rune Enforcer : règles, fonctionnement et interactions (MTG)

Law-Rune Enforcer is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

, : Tap target creature with mana value 2 or greater.

How it works : Law-Rune Enforcer

Original English text — Wizards of the Coast / Scryfall

#1May 3, 2019· Wizards of the Coast
Tokens that aren't a copy of something else don't have a mana cost. Anything without a mana cost normally has a mana value of 0.
No other card is named in this ruling.
#2May 3, 2019· Wizards of the Coast
If a permanent has in its mana cost, X is considered to be 0.
No other card is named in this ruling.