While the docket does contain a translation of the Preference Board’s “Guidelines for the Interpretation and Application of Laws” — a document compiled in 2002 that discusses Law 109 — those guidelines do not purport to be definitive with respect to- the law’s scope. To add to the mystery, the local courts have had virtually no occasion to discuss Law 109. Given this apparent void, evidence of custom, usage, and administrative practice is likely to be useful. The statute is now almost twenty years old. If the agencies charged with enforcing its command consistently have interpreted the language one way or another, that fact may prove to be of considerable assistance in determining the statute’s meaning. See Pharm. Research & Mfrs. of Am. v. Concannon, 249 F.3d 66, 75 (1st Cir.2001) (<HOLDING>); Zambrana v. Gonzalez, 145 P.R. Dec. 616, 639
recognizing that deference to an agencys interpretation of the written law is appropriate only when that interpretation is within the written laws language holding that where statute is ambiguous deference is appropriately accorded to agencys interpretation holding that deference is owed to state agencys interpretation of state law holding that an agencys interpretation of its own regulations is entitled to deference holding that deference is owed to an agencys interpretation of its own categorical exclusion regulations so long as that interpretation is not plainly erroneous or inconsistent with the regulation