The practical upshot is equipment. A fixed lead of six feet or less satisfies the federal requirement and works everywhere else in the District, which is a good reason to make it the default rather than something you swap in at a park boundary. Retractable leads are a poor fit for this dog regardless of the rules: they offer almost no control at the moment control is needed, and the difference between a mildly interested 30-pound dog and a mildly interested 150-pound one is not a difference of degree.
The second requirement is manners, which at this weight is a legal matter as much as a social one. This breed's trainability is documented at 3 out of 5 — genuinely responsive to consistency rather than automatic — and the skills that count in a city this crowded are walking without pulling, settling on cue, and disengaging from distractions. Those are teachable, and they are far easier to teach at forty pounds than at a hundred and forty.
The good news is that the underlying temperament fits. Documented as gentle, patient and watchful, rated 4 out of 5 with strangers and 4 out of 5 with other dogs, this is not a breed that wants trouble on a crowded path.