Copyrighted? Yes. Enforceable? Probably not. In the USA, the copyrighted nature of patents and applications for patents would, like anything else, initially depend upon when and how it was created and published. Prior to 1989 the publication was required to have a "proper copyright notice" or registration, but that is no longer the case. Works of US authors published prior to 1989 without copyright notice or the required registration automatically lost their copyrights to the public domain. Some older patents do, in fact, contain copyright notices, under 37 CFR 1.71(d) or 1.84(s).
Published works of foreign authors are subject to different rules, such as 17 USC 104A, restoring US copyright in certain works where their US publications failed to adhere to all US copyright formalities (notice, renewal).
Some people are confused that "patents" are "government publications" and thus "public domain" for that reason. This is not true of publications for which the authors were not officers or employees of the US government. 17 USC 105.
The US Copyright Office will, in fact, register claims for copyright in such things.
717.3 Patents, Patent Applications, and Non-Patent Literature
Copyright Office may register a claim to copyright in the written
description for an invention or the drawings or photographs set forth
in a patent or a patent application, provided that the work contains a
sufficient amount of original authorship. Likewise, the Office may
register a claim to copyright in articles, publications, or other
non-patent literature that may be submitted with a patent application.
However, the copyright in a patent, a patent application, or
non-patent literature does not extend to any “idea, procedure,
process, system, method of operation, concept, principle, or
discovery” that may be disclosed in these works. 17 U.S.C. § 102(b).
Compendium of U.S. Copyright Office Practices, Third Edition, 2014, p.408.
Whether a federal court might limit the enforcement of such copyright would be a different question. The applicant for a patent may have granted an implied license for the entire world to duplicate and distribute the work, not to mention that an issued patent may have similar status to a statute that defines the parameters of unlawful conduct, and strong public policies to encourage widespread dissemination. It may also be hard to find a use of a patent text or drawing that is not also "fair use", under the overriding public policy concerns.
Bottom line: it is axiomatic that "a right without a remedy is not a right at all", meaning that if you cannot enforce it, such a right is meaningless.