Bride's Gown — ruling 1

In the phrase “as long as an Equipment named . . . is attached to a creature you control,” the “you” is the controller of the Equipment, not the controller of the creature it's attached to. Suppose an opponent controls a creature equipped with Bride's Gown and another creature equipped with Groom's Finery, and they also control both of those Equipment. If you gain control of one of those creatures but not the Equipment attached to it, the creature you gained control of will get all the bonuses and the creature they control will only get +2/+0.

Bride's Gown : règles, fonctionnement et interactions (MTG)

Bride's Gown 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

Equipped creature gets +2/+0. It gets an additional +0/+2 and has first strike as long as an Equipment named Groom's Finery is attached to a creature you control. Equip (: Attach to target creature you control. Equip only as a sorcery.)

How it works : Bride's Gown

Original English text — Wizards of the Coast / Scryfall

#1November 19, 2021· Wizards of the Coast
In the phrase “as long as an Equipment named . . . is attached to a creature you control,” the “you” is the controller of the Equipment, not the controller of the creature it's attached to. Suppose an opponent controls a creature equipped with Bride's Gown and another creature equipped with Groom's Finery, and they also control both of those Equipment. If you gain control of one of those creatures but not the Equipment attached to it, the creature you gained control of will get all the bonuses and the creature they control will only get +2/+0.
Card named in this ruling
Groom's Finery Groom's Finery

Interactions with other cards

These cards' text mentions Bride's Gown.

Groom's Finery

Equipped creature gets +2/+0. It gets an additional +0/+2 and has deathtouch as long as an Equipment named Bride's Gown is attached to a creature you control. Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)