If you're playing standard D&D, I don't think that restriction is in place, particularly because standard D&D tends to stay based on the Prime Material Plane and doesn't tend to bother with extraplanar matters in detail.
However, if you're running Planescape, or a variant of it, that is completely different.
The Planewalker's Handbook, pg. 110.
More than any other type of item, magical weapons, armor, and items with bonuses (pluses) of any kind are bound to the magic of their plane of origin. Such creations are attuned to the energies of that plane, and diminish in power if they're taken from it. The further the item moves from its plane of origin, the less powerful its enchantment, at least for the duration of the separation.
For each plane removed, the item subtracts one from its bonus. For example, if a battle-axe +3 forged in Sigil is taken from Sigil to Elysium, it becomes a battle-axe +2, being one plane removed. If the same axe is then taken to the Ethereal Plane, it becomes a battle-axe +0, tracing three steps from Sigil through the Astral to the Prime to the Ethereal.
Unfortunately, I don't know what setting your DM is running. Your cleric may simply be referencing this rule as he remembers it from AD&D Planescape. (Which proves he's not just some clueless berk!) This is understandable, as Planescape rules (even though they're outdated) are frequently adapted and referenced as a well-defined ruleset for the plane-traveling part of a standard D&D campaign. Planescape is, after all, the binding tie between all the other D&D fantasy settings and the Planes.
Something to note about the rule itself and balance in the game vs. flavor of the setting
That particular rule was not well balanced for AD&D at the time, much less later editions. Even though he is correct in remembering that this rule did exist at one time, it is probably not a good idea to houserule it back into existence for a variety of reasons. Even at the time, many of us early Planescape gamers houseruled that rule OUT of the Planescape setting because of added complexity without much added depth. To maintain the flavor, though, my group ruled that a magic item was instead more powerful on its plane of origin. This minimized the complexity while retaining the basic idea in the lore. Also, from a "fun" aspect, bonuses feel better than penalties.