"unless it be" is correct and usable in written English.
You can use it to suggest the possible exception to a general rule. For example, "No one is allowed in the park after dark, unless it be for an emergency."
"What we are staying here for I am utterly at a loss to know," General William Nott wrote, "unless it be to be laughed at by the Afghans and the whole world".
New babies in any family, while no doubt positively valued, will not usually be judged under Capacity (unless it be negative), Normality (positive/negative according to the usuality of the behaviour), Tenacity (positive/negative according to 'appropriateness' of inclination/psychological disposition), or Propriety (positive/negative according to ethical codes).
Certainly a failure to afford a fair hearing, which is the very essence of the duty to act fairly, can never of itself be regarded as not of "sufficient substance" unless it be because of its perceived effect on the result or, in other words, the actual prejudice caused by it.
A note discounted at a bank, when not paid in whole or in part, is not usually surrendered to a third party without a valuable consideration, unless it be for collection, or to obtain its renewal, or security for it; and such usual action should be negatived by averment.
No further changes will be made (unless it be by Columbia administration).
Though I prove them ever so guilty, I shall not, therefore, advise their death, unless it be expedient; nor though they should have claims to indulgence, shall I recommend it, unless it be dearly for the good of the country.
Ct. 273, 31 L. Ed. 205; unless it be the advantage of living and doing business in a civilized community.
And there should be no flag waving, unless it be the lowering of the flags of all the nations who lost their sons, unless it be to celebrate the peace we now share together, unless it be to reaffirm again our determination to guard our freedom, but as far as humanly possible to do it in peace.
There should be no flag waving, unless it be the lowering of the flags of all the nations who lost their sons, unless it be to celebrate the peace we now share together, unless it be to reaffirm again our determination to guard our freedom, but as far as humanly possible to do it in peace.
In the case of a joint author, there is no one for whom a joint author can take the copyright vicariously, unless it be his joint author.
For (1) an accident is not an accident of an accident, unless it be because both are accidents of the same subject.
